For aesthetic reasons, it may be desirable for a door skin to have two adjacent half-round curvatures, i.e., curvatures of greater than 90 degrees. Metal doors are known to have such configurations. Metal doors, however, can be damaged somewhat easily, for example, by denting. Additionally, metal doors can be heavy to ship, cumbersome to install, and costly.
Fiberglass doors are also known to have adjacent, sharp curved portions. While fiberglass is not damaged easily and is light-weight compared to metal, it is one of the more costly materials to use for doors. Furthermore, over time, ultraviolet light degrades the coating of the fiberglass door, and ultimately, destroys the face of the door.
Fiberboard door skins have the advantages of being economical, not easily damaged, and durable over time. However, when forming fiberboard door skins with curvatures greater than 90 degrees, proper surface consistency and density have been extremely difficult to achieve. When a fiberboard mat is molded, i.e., stretched, to include two adjacent bends of at least 90 degrees, the added contours increase the amount of surface distance of the mat compared to a substantially flat mat. Stretching the fiberboard mat farther than desirable, i.e., over-stretching, results in surface discontinuities and flaws such that paint, stains, and other finishes do not properly adhere to the surface of the mat.
Prior attempts at forming fiberboards having two adjacent half-round curvatures as described below have resulted in door skins being either too porous or too dense. In regions where the skin is too porous, i.e., the density is too low, paint, stains, and other finishes do not adhere to the surface but rather, are absorbed by the wood. Such surfaces appear rough or uncovered.
In regions where such a skin has an unusually high density, the surface blisters and cracks. Paint, stains, and other finishes cannot adhere to such surfaces, and generally appear darker when compared to other regions where the density is within acceptable ranges. A door surface having such an uneven appearance is generally considered to be aesthetically unpleasing. Additionally, there are discontinuities and flaws in the surfaces of such door skins in such situations.
Attempts have been made to compensate or correct for such density extremes. One such attempt includes increasing the density of regions where low densities are expected when molding the door skin. This approach, while successful in gradual curvatures of the surface, such as, for example, quarter curves, has not been successful for the curvatures described above. Blistering and cracking of the surface still occurs in this approach.
Other approaches have been attempted, and have been unsuccessful as well. Once a fiberboard door skin has been formed with a density that is either too low or too high, there are no known solutions to remedy or correct problems with the surface appearance and consistency of door skins. Thus, such door skins must be discarded, which ultimately increases the costs of door production.